parsingtree.h

编译原理的语法分析器

#ifndef ParsingTree
#define ParsingTree

//function will be used,,,
char ignorspace(char c)
{
	while(isspace(c)) {c=nextchar();}
	return c;
}

char tempchar;  //check the position of error
char match(char c1)
{ 

	c=nextchar();  
	c=ignorspace(c);
	
	if(c==c1){
		printf("< TERMINAL,%c>\n",c);
		//	return 1;
	}
	else {
		
		tempchar=retract(1);
		while(isspace(tempchar)){tempchar=retract(1);}
		
		printf("\nError after CHRACTER '%c' !\n\n",tempchar);
		//	tempchar=nextchar();
		exit(0);
	}
	return c;
}


char checkchar[6]; //check match
int matchend=0;
int matchdo=0;
int matchthen=0;
int matchelse=0;



//construct the parsing tree here...
char list()
{
	printf("list->stmt list'\n");
    //---------
	state=9;                  
	c=nextchar();
	c=ignorspace(c);
	c=retract(1);
	c=nexttoken();

	stmt();           
	c=nextchar();
	list1();
    //  printf("list ......finished!\n");
	return c;
}
char list1()
{
	c=ignorspace(c);                  
	if(c=='\0') 
	{
		printf("list'->ε\n");
	}
	else if(c==';')
	{
		c=retract(1);
		printf("list->; stmt list'\n");
		match(';');
	   //------------
		state=9;                  
		c=nextchar();
		c=ignorspace(c);
		if(c=='\0')
		{
			printf("\n\nYou have printed';' at the end of list,\npls construct another list OR erase ';'\n\n");
			exit(0);
		}
		c=retract(1);
		c=nexttoken();



		stmt();

		c=nextchar();
		list1();
	}	
	else if(isalpha(c)&&(matchend>0))
	{
		c=retract(1); 
        printf("list'->ε\n");
	}
	else 
		//(!isalpha(c))  //if it's not alphabet  e.g the character like '!@#$%^'
	{
		printf("\n\nError CHARACTER '%c' !\n",c);
		printf("To recover this mistake..\nYou can match ';' between two CHARACTERS to construct another statement,\nOr erase the space between them!\n");
		exit(0);
		
	}
	return c;
}
void MatchBeginEnd()
{
	matchend++;
//	printf("stmt->BEGIN list END\n");
	printf("< TERMINAL,%s>\n",alp);//keywords
	list();  
	//	printf("prepare  matchend is ..%d\n",matchend);
	if(matchend!=0)  //match end
	{
		state=9;
		c=nexttoken();
		c=ignorspace(c);
		if(strcmp(alp,"end")==0)
		{
			printf("< TERMINAL,%s>\n",alp);
			matchend--;   //match over 
		}
		else //if the character is alphabet but there's space between them (except 'end')
		{
			printf("\n\nError on Spacekey!\nPls match ';' between two CHARACTERS to construct another statement,\nOr erase the space between them!\n");
			exit(0);
		}
	}	
}

void MatchIfThenElse()
{
	printf("stmt->IF expr THEN stmt elsestmt\n"); 
	matchthen=1;
	printf("< TERMINAL,%s>\n",alp);
	c=nextchar();
	c=ignorspace(c);

	expr(1);
	
	state=9;                      
	c=nextchar();
	c=ignorspace(c);
	c=retract(1);
	c=nexttoken();
	if(matchthen!=0)
	{
		//MatchThen();	
		if(strcmp(alp,"then")==0) 
		{
			printf("< TERMINAL,%s>\n",alp);
			matchthen=0;
			matchelse++;
			
			//	printf("stmt->IF expr THEN stmt\n\;n")
			//-------------
			state=9;                  
			c=nextchar();
			c=ignorspace(c);
			c=retract(1);
			c=nexttoken();
			stmt();
 
			if(matchelse!=0)
			{
				c=nextchar();
				c=ignorspace(c);
  
			//	if(strcmp(alp,"else")==0)
				if(c=='e')				
				{
				    c=nextchar();
					if(c=='l')
					{
						c=nextchar();
						if(c=='s')
						{
							c=nextchar();
							if(c=='e')
							{
								c=nextchar();
								if(isspace(c))
								{
					  //printf("stmt->IF expr THEN stmt ELSE stmt\n\n");
						 printf("elsestmt->else stmt\n");		
						 printf("< TERMINAL,else>\n");
						 matchelse--;
						//------------
					      state=9;                  
					      c=nextchar();
					      c=ignorspace(c);
					      c=retract(1);
					      c=nexttoken();
					      stmt();
								}
								else//not spacekey
								{
									c=retract(5);
									printf("elsestmt->ε\n");
								}
							}
							else// not e
							{
								c=retract(4);
								printf("elsestmt->ε\n"); 
							}
						}
						else//not s
						{
							c=retract(3);
							printf("elsestmt->ε\n"); 
						}
					}
					else//not l
					{
						c=retract(2);
                        printf("elsestmt->ε\n");
					}
				}//not e
				 else
				{
				   c=retract(1);
				   printf("elsestmt->ε\n");   
				}
			}
			/**/
           //else  no 'else' to match
		}
		else 
		{
			printf("\n\nError!\nPls match 'then' before '%s%s' to construct another statement,\nOr erase the space between them!\n",alp,digit);
			exit(0);
		}
	}
}

char stmt()
{
    if(strcmp(alp,"if")==0) // if expr then stmt (else stmt)
	{          
		MatchIfThenElse();
	}
	else if(strcmp(alp,"while")==0)    //stmt->WHILE expr DO stmt
	{                  	
		matchdo=1;
		printf("stmt->WHILE expr DO stmt\n");             
		printf("< TERMINAL,%s>\n",alp);

			c=nextchar();
	        c=ignorspace(c);

			expr(1);

            //match do
			state=9;                      
			c=nextchar();
			c=ignorspace(c);
			c=retract(1);
			c=nexttoken();
			if(matchdo)
			{
				if(strcmp(alp,"do")==0) 
				{
					printf("< TERMINAL,%s>\n",alp);
					matchdo=0;// match over ...close..

					state=9;                  
					c=nextchar();
					c=ignorspace(c);
					c=retract(1);
					c=nexttoken();

					 stmt(); 
				}
				else 
				{
					printf("\n\nError!\nPls match 'do' before '%s%s' to construct another statement,\nOr erase the space between them!\n",alp,digit);
					exit(0);
				}
			}		
	}
	else if(strcmp(alp,"begin")==0)         //stmt->BEGIN list END
	{
		 MatchBeginEnd();		
	}
	else if(isk==1)                     // stmt->ID:=expr
	{		
	         // c5=0;    
		      printf("stmt->ID:=expr\n");
		//	  printf("stmt->ID:=expr%d\n",etimes);
		      printf("< ID,%s>\n",alp);

			  match(':'); 
			  match('=');
			  c=nextchar();
			  expr(1);		
	}
	return c;
}

char expr(int e)                   
{
	if(e){

//		printf("expr%d->term%d expr%d\n",etimes,ttimes,etimes+1);
		printf("expr->term expr'\n");
        term(1);
		c=nextchar();
        expr1();
		}
	return c;
}
char expr1()                             
{                        
    c=ignorspace(c);
	if(c=='+') {
		printf("expr'->+ term expr'\n");
		c=retract(1);
		match('+');
		c=nextchar();
		term(1);
		c=nextchar();
		expr1();
	}
	else 
	{
		printf("expr'->ε\n");
		c=retract(1);	            
	}
	return c;
}

char term(int t)                        
{
	if(t) 
	{  		
		printf("term->factor term'\n");
//		printf("term%d->factor term%d\n",ttimes,ttimes+1);
        factor();
		c=nextchar();
	                       
		term1();
	}
	return c;
}
char term1()
{
	c=ignorspace(c);
	if(c=='*')
	{
		
		printf("term'->* factor term'\n");
		c=retract(1);
		match('*');
		c=nextchar();
		factor();
		c=nextchar();
		term1();
	}
	else //not '*' ,consider as ε,and  just skip it     
	{	
		printf("term'->ε\n");
		c=retract(1);
	}   
    return c;
}

char factor()                             
{  
	c=ignorspace(c); 
	    //while(isspace(c)) {c=nextchar();}
                                         
	if(isdigit(c)){	                               
		printf("factor->NUM\n");
		c=retract(1);                                  
		state=25;     //12  20  25     	 		
		c=nexttoken();

		printf("< NUM,%s>\n",digit);                                  	
	}
	else if(isalpha(c))        //state 9 to 11
	{	            
		printf("factor->ID\n");
		c=retract(1);	
		state=9;    
		c=nexttoken();     

		if(isk==1)
		{
			printf("< ID,%s>\n",alp);  //check ...here............
		}
		else
		{
			printf("\n'%s' is keyword or illegal!\n",alp);
				exit(0);
		}
	}
	else if(c=='(')
	{
		printf("factor->( expr )\n");
		c=retract(1);
		match('(');
		c=nextchar();
		                  
		expr(1);
                            		
		c=nextchar();
		c=retract(1);
                          
		match(')');	
	}
	else //not '('  ,alphabet , digit
	{
		printf("\nError on evaluation!\nPls use alphabet as ID ,digit as NUM,\nOr MATCHED PARENTHESIS to construct some expressions\n");    //evaluation wrong 
		exit(0);
	}
	return c;
}


#endif